EP0050285B1 - Incorporable reactive blowing agents containing mixtures of polyols, and their use in the production of foamed polyurethanes - Google Patents

Description

The invention relates to mixtures of polyols which are liquid at room temperature with functional aldoximes as blowing agents, the aldoxime groups reacting with polyisocyanates with the elimination of carbon dioxide and at the same time being incorporated into the resulting polyurethane via their functional group. For this reason, the aldoximes are also referred to as ready-to-install reactive blowing agents. The invention further relates to a process for the production of polyurethane foams using these ready-to-install reactive blowing agents as exclusive blowing agent components or in combination with blowing agents known per se in polyurethane chemistry.

The process according to the invention explained below is suitable for the production of any polyurethane foams or cellular polyurethane elastomers, but is preferably used in the production of semi-hard and hard polyurethane foams with a thickened outer skin, which are also referred to as integral foams and by foaming the reaction mixture in closed molds be preserved.

The production of such integral polyurethane foams is known in principle and z. B. described in DE-AS 1 196 864. It takes place e.g. B. by filling a reactive and foamable mixture based on compounds with several, reactive towards NCO groups hydrogen atoms and polyisocyanates in a closed form. According to the prior art, water and / or fluorocarbons are used as blowing agents. Catalysts such as are known per se for polyurethane foam production are generally also used.

By suitable choice of the starting component, in particular by choice of the molecular weight and the functionality, it is possible to produce both elastic and rigid or all variants of foams lying between these groups. The dense outer skin is achieved in this process in that a larger amount of foamable mixture is introduced into the mold than would be necessary to fill the mold interior volume by free foaming. The inner mold wall generally cools the reaction mixture and condenses the preferably organic blowing agent, so that the blowing reaction on the inner mold wall comes to a standstill and the compact outer skin is formed.

Only technically fluorinated and / or halogenated hydrocarbons are suitable as organic blowing agents for this process, since on the one hand they have a sufficiently low boiling point and on the other hand they do not form explosive gas mixtures when mixed with air. For the latter reason z. B. the use of pentane as a propellant is inappropriate because expensive safety precautions are necessary because of the low explosion limit of pentane-air mixtures. Proven blowing agents for integral polyurethane foams are especially fluorotrichloromethane and / or methylene chloride.

From an ecological point of view, concerns about both blowing agents have recently been raised.

It is therefore desirable to develop blowing agent alternatives for the production of polyurethane foams, especially for integral polyurethane foams.

As already mentioned, water can be used as a blowing agent generator in the polyurethane system. Using this variant, polyurethane free foams of excellent quality can be produced, but not integral foams, since both the surface quality and the integral structure of the foam deteriorate compared to integral molded parts foamed with fluorocarbons, as is known to the person skilled in the art. Another disadvantage is that the water as an individual component must be metered into the reactive mixture only immediately before the foaming, since when appropriate amounts of water are added to the polyol component, which generally already contains the foaming catalyst, an at least partial saponification of the tin compounds indispensable as a catalyst, e.g. B. of dibutyl (IV) dilaurate occurs, which manifests itself in an uncontrolled decrease in activity of the fully activated polyol component. Other blowing agent variants are compounds which disintegrate at temperatures above room temperature and thereby release a blowing gas. Examples are azodicarbonamide, azo-bis-isobutyronitrile or diphenylene oxide disulfohydrazide as nitrogen releasers and the pyrocarbonates described in DE-OS 2 524 834 (US Pat. No. 4,070,310) and the benzooxazines claimed in DE-AS 2 218 328 which release CO _z . In order to be able to use them for the intended purpose, these compounds must have a relatively low decomposition temperature, which, according to general experience, should be well below 100 ° C. This is because the blowing agents must be effective right at the start of the urethanization reaction. At this point, however, there is still no excessive heat generation in the reaction mixture. However, compounds with such a low decomposition temperature are naturally sensitive during storage and require careful treatment, which in many cases cannot be guaranteed in the technical process by the processors of polyurethane foams. In addition, it is often characteristic of these compounds that there is an uncontrolled decay during storage, so that they also represent a safety risk that should not be underestimated.

In DE-PS 1 112 285 (GB-PS 908 337) the use of alkanaldoximes as blowing agents mentioned. The aldoximes react with NCO groups with elimination of C0 ₂ . At the same time, however, the corresponding alkyl nitrile forms, in the case of the representatives mentioned there: acetaldoxime, butyraldoxime or isobutyraldoxime, correspondingly the aceto-, butyro- or isobutyronitrile, which are all physiologically questionable and have low flash points.

As has now been found, the disadvantages of the prior art described can be remedied by adding functional aldoximes to the known foamable mixtures of the prior art, ie aldoximes which contain a further group which is reactive toward NCO groups, such as, for. B. -OH, -NHR-, Ar-NH ₂ , -SH, -COOH or epoxy or carboxylic acid anhydride groups. Hydroxyl groups, carboxyl groups and aromatically bound amino groups bonded to (cyclo) aliphatic radicals are preferred as functional reactive groups. Secondary hydroxyl groups bonded to (cyclo) aliphatic radicals are very particularly suitable. These ready-to-install aldoxime reactive blowing agents can be stored in the polyol mixture practically indefinitely. As a rule, they do not lead to the hydrolysis of tin catalysts and thus also to no loss of activity of the fully activated polyol mixture; the hydroxyl group-containing aldoxime blowing agents are particularly suitable here, since they are completely stable with respect to the tin catalysts. The splitting off of C0 ₂ , which causes the foam blowing reaction, takes place only when polyisocyanates are added to the reaction mixture. The mixtures can be processed in an environmentally friendly and harmless manner, since the products formed from the reactive blowing agent during the reaction are incorporated into the polyurethane without any deterioration in the polyurethane properties being observed.

• A) unterhalb von 45°C flüssige Polyole oder Polyolgemische mit einem mittleren Molekulargewicht von 400 bis 10 000; und darin gelöst
• B) 0,1 bis 20 Gew.-%, vorzugsweise 0,2 bis 8 Gew.-% eines einbaufähigen Aldoxim-Reaktivtreibmittels der Formel
  
  wobei
  • X -OH, -COOH, -NH₂ (Amin nur an aromatische Reste gebunden), -NHR', worin R' eine Alkylgruppe mit 1 bis 8 C-Atomen bedeutet (nur an aromatische Reste gebunden); vorzugsweise die OH-Gruppe, besonders als sekundäre OH-Gruppe, und
  • R einen aliphatischen, gegebenenfalls verzweigten Rest mit 1 bis 9 C-Atomen, vorzugsweise 1 bis 4 C₄-Atomen, einen cycloaliphatischen Rest, gegebenenfalls ein -O-Atom im Ring enthaltend, einen aromatischen Rest oder einen araliphatischen Rest, bei dem der aliphatische Rest durch ein Sauerstoffatom an den aromatischen Kern gebunden ist, bedeutet.

The invention relates to mixtures containing aldoximes as blowing agents

• A) below 45 ° C liquid polyols or polyol mixtures with an average molecular weight of 400 to 10,000; and solved in it
• B) 0.1 to 20 wt .-%, preferably 0.2 to 8 wt .-% of a buildable aldoxime reactive blowing agent of the formula
  
  in which
  • X -OH, -COOH, -NH ₂ (amine only bound to aromatic radicals), -NHR ', in which R' denotes an alkyl group with 1 to 8 C atoms (only bound to aromatic radicals); preferably the OH group, especially as a secondary OH group, and
  • R is an aliphatic, optionally branched radical having 1 to 9 C atoms, preferably 1 to 4 C ₄ atoms, a cycloaliphatic radical, optionally containing an -O atom in the ring, an aromatic radical or an araliphatic radical in which the aliphatic radical Radical is bonded to the aromatic nucleus by an oxygen atom.

• A) unterhalb von 45° C flüssigen Polyolen oder Polyolgemischen mit einem mittleren Molekulargewicht von 400 bis 10 000; und darin gelöst
• B) 0,1 bis 20 Gew.-%, vorzugsweise 0,2 bis 8 Gew.-% eines einbaufähigen Aldoxim-Reaktiv-Treibmittels der Formel
  
  zur Umsetzung mit Polyisocyanaten, gegebenenfalls in Gegenwart weiterer Verbindungen vom Molekulargewicht 62 bis 10 000, vorzugsweise 62 bis 400, mit gegenüber NCO-Gruppen reaktiven H-Atomen,

unter Bildung von Polyurethanschaumstoffen.The invention also relates to the use of mixtures of

• A) below 45 ° C liquid polyols or polyol mixtures with an average molecular weight of 400 to 10,000; and solved in it
• B) 0.1 to 20 wt .-%, preferably 0.2 to 8 wt .-% of a buildable aldoxime reactive blowing agent of the formula
  
  for reaction with polyisocyanates, optionally in the presence of further compounds with a molecular weight of 62 to 10,000, preferably 62 to 400, with H atoms reactive towards NCO groups,

with the formation of polyurethane foams.

Examples of these functional aldoxime blowing agents of the formula:

Particularly suitable as blowing agents and preferred for the process according to the invention for the production of polyurethane foams are aldoximes with secondary hydroxyl groups. A particularly preferred compound is 3-hydroxybutanaldoxime (1), which is also easily accessible industrially. The polyurethane free foams produced with these secondary hydroxyl group-containing aldoximes have lower densities than foams produced with aldoximes with primary hydroxyl groups or with amino groups. Furthermore, no disturbances in the free foam occur when using aldoximes with secondary hydroxyl groups, whereas when using with aldoximes with primary hydroxyl or amino groups, cracks and surface defects are sometimes observed in the finished foam. However, the compounds can likewise be used with advantage for the production of integral foams.

For the preparation of the mixtures of polyols and aldoxime reactive blowing agents (1) which contain aldoxime blowing agents, all polyols or polyol mixtures which are customarily used and which have a low melting point of less than 45 ° C. but are preferably liquid are suitable.

The preparation of the blowing agent-containing mixtures is per se unproblematic and can be achieved simply by stirring the ready-to-install aldoxime reactive blowing agents in the polyols, heating up to about 60 ° C. can accelerate the dissolution. However, it is also possible to dissolve the blowing agents in a subset or in one of the polyol components, e.g. B. in low molecular weight diols in 1,4-butanediol and then mix with the main polyol. Other auxiliaries such as catalysts, leveling agents and pigment pastes can optionally be mixed in.

As the polyol starting components for the cellular polyurethanes or the polyurethane foams including integral foams, compounds with at least two isocyanate-reactive hydrogen atoms and a molecular weight of from 62 to 10,000 are generally used in the individual components. The predominant amount is preferably replaced by compounds having hydroxyl groups, in particular 2 to 8 higher molecular weight compounds having hydroxyl groups, especially those having a molecular weight of 400 to 8000, preferably 600 to 4000. These are e.g. B. 2, usually 2 to 8, but preferably 2 to 4, hydroxyl-containing polyesters, polyethers, polythioethers, polyacetals, polycarbonates and polyesteramides or mixtures thereof, as are known per se for the production of homogeneous and cellular polyurethanes. They can be mixed with other, low molecular weight, polyfunctional compounds such as preferably polyols, but optionally also polyamines or polyhydrazides with molecular weights of about 62 to 400 in order to modify the properties of the polyurethanes. However, the predominant proportion in the polyol mixture (for example more than 60% by weight, preferably more than 80% by weight) are the higher molecular weight polyols with molecular weights from 400 to 10,000, preferably from 600 to 4000. The middle Molecular weight of the polyol mixtures of high molecular weight and optionally low molecular weight polyols should be between 400 and 10 OOO, preferably between 600 and 4000, if cellular polyurethane elastomers and preferably polyurethane foams, including molded foamed integral foams, are to be produced.

The preferably used, at least 2, usually 2 to 8, preferably 2 to 3, hydroxyl-containing polyethers are those of the type known per se and are known, for. B. by polymerization of tetrahydrofuran or epoxides such as ethylene oxide, propylene oxide, butylene oxide, Styrene oxide or epichlorohydrin with itself, e.g. B. in the presence of Friedel-Crafts catalysts such as boron trifluoride, or by addition of these alkoxides, preferably of ethylene oxide and propylene oxide, optionally in a mixture, for. B. in a ratio of 5: 95 to 95: 5, or in succession, of starting components with reactive hydrogen atoms such as water, alcohols, ammonia or amines, for. B. ethylene glycol, propylene glycol, ethylene glycol, propylene glycol-1,3 or -1,2, trimethylolpropane, glycerol, sorbitol, 4,4'-dihydroxydiphenylpropane, aniline, ethanolamine or ethylenediamine. Succhrose polyethers as well as formit or formose-started polyethers are also suitable. In many cases, those polyethers are preferred which predominantly (up to 90% by weight, based on all the OH groups present in the polyether) have primary OH groups. Polybutadienes containing OH groups are also suitable.

Suitable hydroxyl-containing polyesters are e.g. B. reaction products of polyhydric, preferably dihydric, and optionally additionally trihydric alcohols with polyhydric, preferably dihydric, carboxylic acids. The polycarboxylic acids can be aliphatic, cycloaliphatic, aromatic and / or heterocyclic in nature and optionally, e.g. B. by halogen atoms, substituted and / or unsaturated. Examples of such carboxylic acids and their derivatives are: adipic acid, sebacic acid, isophthalic acid, trimellitic acid, phthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylene tetrahydrophthalic anhydride, fumaric acid, di- or trimerized unsaturated fatty acids, unsaturated fatty acid monomers, with unsaturated fatty acids, glycol ester. As polyhydric alcohols such. B. ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, butylene glycol-2,3, hexamethylene diol, octamethylene diol, neopentyl glycol, 1,4-bis-hydroxymethyl-cyclohexane, 2-methyl-1,3-propanediol, glycerol, trimethylol propane, hexanetriol- (1 , 2,6), trimethylolethane, pentaerythritol, sorbitol, formite, methylglycoside, also diethylene glycol, triethylene glycol, tetraethylene glycol and higher polyethylene glycols, dipropylene glycol, higher propylene glycols and dibutylene glycol and higher polybutylene glycols in question. The polyesters may have a proportion of terminal carboxyl groups. Lactone polyester, e.g. B. _E -caprolactone, or from hydroxycarboxylic acid, e.g. B. w-hydroxycaproic acid can be used. Mixtures of at least 2 polyols or at least 2 carboxylic acids are preferably used to achieve liquid polyester polyols.

As polyacetals such. B. the compounds which can be prepared from glycols such as di-, tri- or tetraethylene glycol, 4,4'-dioxethoxydiphenyldimethylmethane, hexanediol and formaldehyde or trioxane.

Suitable polycarbonates having hydroxyl groups are those of the type known per se, such as, for. B. by reacting diols such as 1,3-propanediol, 1,4-butanediol or 1,6-hexanediol, di-, tri- or tetraethylene glycol with diaryl carbonates or phosgene. The polyhydroxyl compounds mentioned can be modified in various ways before they are used in the polyisocyanate polyaddition process, for. B. by further esterification or etherification of already pre-formed segments, by reaction with a less than equivalent amount of a diisocyanatocarbodiimide and subsequent reaction of the carbodiimide group with an amine, amide, phosphite or carboxylic acid. If appropriate, it is also possible to use polyhydroxyl compounds which contain high molecular weight polyadducts and polycondensates or polymers in finely dispersed or dissolved form. Such polyhydroxyl compounds are e.g. B. obtained when polyaddition reactions (z. B. reactions between polyisocyanates and amino-functional compounds) or polycondensation reactions (z. B. between formaldehyde and phenols and / or amines) in situ in the above. Hydroxyl-containing compounds can run off. Also modified by vinyl polymers polyhydroxyl compounds, such as z. B. by polymerization of styrene and acrylonitrile in the presence of polyethers or polycarbonate polyols are suitable for the inventive method. When using modified polyhydroxyl compounds of the above. Kind as starting components in the polyisocyanate polyaddition process in many cases, polyurethane foams with significantly improved mechanical properties. Of course, mixtures of the above. Hydroxyl compounds with at least two isocyanate-reactive hydrogen atoms with an average molecular weight of 400 to 10,000, for. B. mixtures of polyethers and polyesters, optionally in an additional admixture of low molecular weight polyols. An even more detailed list of suitable polyhydroxyl compounds is given on pages 11 to 21 of DE-OS 2 854 384.

Aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates can be used as polyisocyanates, as are usually used for the production of polyurethane plastics.

Examples are 1,6-hexamethylene diisocyanate, 1,12-dodecane diisocyanate, methyl caproate 2,6-diisocyanate, any mixtures of the position or stereoisomers of 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclo-hexane, 2 , 4- and 2,6-hexahydrotoluenediisocyanate, hexahydro-1,3-and / or -1, 4-phenylene-diisocyanate, perhydro-2,4'- and / or 4,4'-diphenylmethane diisocyanate, also 1, 3- and 1,4-phenylene diisocyanate, 2,4- and / or 2,6-tolylene diisocyanate, diphenylmethane-2,4'- and / or -4,4'-diisocyanate and its alkyl derivatives, as well as naphthylene-1,5- diisocyanate. Furthermore come in Question: Polyphenyl-polymethylene-polyisocyanates, as obtained by aniline-formaldehyde condensation and subsequent phosgenation and z. B. be described in GB-PS 874430 and 848671, carbodiimide groups containing polyisocyanates, allophanate groups or isocyanurate groups or urethane groups or biuret groups containing polyisocyanates, and polyisocyanates prepared by telomerization reactions. Further suitable polyisocyanates are listed in detail in German Offenlegungsschrift 2854384 on pages 8 to 11. It is also possible to use any mixtures of the aforementioned polyisocyanates.

The technically easily accessible polyisocyanates, e.g. B. the 2,4- and / or 2,6-tolylene diisocyanate (TDI), polyphenyl-polymethylene polyisocyanates, such as those produced by aniline formaldehyde condensation and phosgenation (crude MDI) and carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups Polyisocyanates (modified polyisocyanates), especially those modified polyisocyanates which are derived from 2,4- and / or 2,6-tolylene diisocyanate or from 4,4'- and / or 2,4'-diphenylmethane diisocyanate.

Optionally, other compounds with at least two isocyanate-reactive hydrogen atoms and a molecular weight of 62 to 400 can also be used as reactive components for the polyol mixtures. In this case, too, this is understood to mean especially hydroxyl groups, but also amino groups and / or thio groups and / or carboxyl groups and / or hydrazide end groups, which are referred to as chain extenders or crosslinking agents. These compounds generally have 2 to 8, preferably 2 to 4, hydrogen atoms which are reactive toward isocyanates, in particular hydroxyl groups. In this case, too, mixtures of various such compounds with a molecular weight of 62 to 400 can be used.

Examples of such compounds are: ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, butylene glycol-2,3, pentamethylene glycol, hexamethylene glycol, neopentyl glycol, 1,4-bis-hydroxy-methyl-cyclohexane, 2-methyl-1,3-propanediol, Dibromobutene diol, trimethylolpropane, pentaerythritol, quinite, sorbitol, castor oil, diethylene glycol, higher molecular weight polyethylene glycols with a molecular weight up to 400, dipropylene glycol or higher polypropylene glycols with a molecular weight up to 400, dibutylene glycol, as well as its higher oligomers with a molecular weight up to 400, 4,4'-di'-di diphenylpropane, di-hydroxy-ethyl-hydroquinone, but also ethanolamine, diethanolamine, n-methyldiethanolamine, n-tert-butyl-di - (, 8-hydroxy-propyl) -amine, triethanolamine and 3-aminopropanol. Mixtures of hydroxyaldehydes and hydroxyketones (formose) or the polyhydric alcohols (formite) obtained therefrom by reduction are also suitable as low molecular weight polyols. As further examples of such compounds, further compounds are listed on pages 20 to 26 of DE-OS 2 854 384.

Furthermore, monofunctional compounds in proportions of 0.01 to 10% by weight, based on polyurethane solid, can optionally be used as so-called chain terminators, e.g. B. monoamines such as butyl or dibutylamine, stearylamine, N-methyl-stearylamine, piperidine, cyclohexylamine or monoalcohols such as butanol, 2-ethylhexanol, ethylene glycol monomethyl ether.

• Anorganische oder organische Substanzen als Treibmittel, insbesondere Verbindungen wie Methylenchlorid, Chloroform, Vinylidenchlorid, Monofluortrichlormethan, Chlordichlordifluormethan, ferner Luft, C0₂ oder Stickoxid. Weitere Beispiele für Treibmittel sowie Einzelheiten über deren Verwendung sind im Kunststoffhandbuch, herausgegeben von Vieweg und Höchtlen, Carl-Hanser-Verlag München, 1966, z. B. auf den Seiten 108 und 109,453 bis 455 und 507 bis 510 beschrieben.

Catalysts of the type known per se can also be used, e.g. B. tertiary amines such as triethylamine, N-methylmorpholine, tetramethylethylenediamine, 1,4-diazabicyclo- (2,2,2) -octane, bis- (dimethylaminoalkyl) -piperazines, dimethylbenzylamine, 1,2-dimethylimidazole, mono - And bicyclic amidines, bis- (dialkylaminoalkyl ethers), and tert-amines having amide (preferably formamide) groups. Mannich bases known per se from secondary amines and aldehydes or ketones can also be used as catalysts. According to the invention, especially organic metal compounds such as organic tin compounds are used as catalysts. In addition to sulfur-containing compounds such as di-n-octyl-tin-mercaptide, the organic tin compounds which are preferably tin (II) salts of carboxylic acids such as tin (11) acetate, tin (11) ethylhexoate and tin (IV) -Connections, e.g. B. dibutyltin dichloride, dibutyltin diacetate, dibutyltin dilaurate or dibutyltin maleate into consideration. Of course, all catalysts can be used as mixtures. Further representatives of usable catalysts and details about the mode of action are in the plastics handbook Volume VII, published by Vieweg and Höchtlen, Carl-Hanser-Verlag, Munich 1966, z. B. described on pages 96 to 102 or listed in DE-OS 2 854 384. The following can be used as auxiliaries and additives:

• Inorganic or organic substances as blowing agents, in particular compounds such as methylene chloride, chloroform, vinylidene chloride, monofluorotrichloromethane, chlorodichlorodifluoromethane, and also air, CO ₂ or nitrogen oxide. Further examples of blowing agents and details of their use are in the plastics handbook, published by Vieweg and Höchtlen, Carl-Hanser-Verlag Munich, 1966, z. B. on pages 108 and 109,453 to 455 and 507 to 510.

Surface-active additives, such as emulsifiers and foam initiators, are also used in the usual way. As emulsifiers such. B. sodium salts of castor oil sulfonates or salts of fatty acids with amines such as oleic acid diethylamine, also alkali metal or ammonium salts of sulfonic acids such as dodecylbenzenesulfonic acid or dinaphthylmethane disulfonic acid in question.

Foam stabilizers in particular are polyether siloxanes, especially water-soluble representatives. Response delay, e.g. B. acidic substances such as hydrochloric acid, chloroacetic acid or orga African acid halides, also cell regulators of the type known per se, such as paraffins or fatty alcohols or dimethylpolysiloxanes, as well as pigments or dyes and / or flame retardants of the type known per se, also stabilizers against aging and weather influences, plasticizers, fungistatic and / or bacteriostatic substances, and also Fillers can also be used. Details of these additives and auxiliaries can be found in DE-OS 2 854 384 on pages 26 to 31 and the references cited therein.

The foam can be produced both as free foam and as molded foam in the usual way. Of course, the foams can also be produced for block foaming or according to double conveyor belt processes known per se or any other variant of foam technology.

Examples example 1 a) Preparation of the mixture containing blowing agent

• 1.) 60 Gew.-Teilen eines Polyethers der OH-Zahl 860, der durch Anlagerung von Propylenoxid an Trimethylolpropan erhalten wurde, und
• 2.) 40 Gew.-Teilen eines Polyethers der OH-Zahl 42, der durch Anlagerung eines Gemisches von Propylenoxid und Ethylenoxid an ein Gemisch aus Trimethylolpropan und Propylenglykol (MolVerhältnis = 3 : 1) erhalten wurde;

100 parts by weight of a polyol mixture having an average hydroxyl number of 500 and a water content of less than 0.3% by weight and a viscosity at 25 ° C. of 2500 mPas, consisting of

• 1.) 60 parts by weight of a polyether of OH number 860, which was obtained by addition of propylene oxide to trimethylolpropane, and
• 2.) 40 parts by weight of a polyether of OH number 42, which was obtained by adding a mixture of propylene oxide and ethylene oxide to a mixture of trimethylolpropane and propylene glycol (molar ratio = 3: 1);

1.0 part by weight of a commercially available polysiloxane-polyalkylene oxide block copolymer as foam stabilizer; 3.0 parts by weight of N-dimethylbenzylamine and 0.5 part by weight of tetramethylguanidine as catalysts; 3.0 parts by weight of amidamine oleic acid salt, prepared from 1 mole of 3-dimethylaminopropylamine-1 and 2 moles of oleic acid, as an internal release agent; 0.2 part by weight of 85% aqueous ortho-phosphoric acid as a reaction retardant and 3 parts by weight of 3-hydroxybutanal oxime (acetaldol oxime) as blowing agent become component A (mixture containing reactive blowing agent according to the invention); Component B consists of a polyisocyanate, which was obtained by phosgenation of aniline-formaldehyde condensates and has a viscosity of 130 mPas at 25 ° C. and an NCO content of 31% by weight (crude MDI).

b) Use of the blowing agent-containing polyol mixture for foam production

103 parts by weight of component A and 146.0 parts by weight of component B are mixed intensively with a two-component metering mixer. This foamable reaction mixture is immediately entered into an open paper form (dimensions: length = 250 mm, width = 120 mm, height = 120 mm). The following reaction times result when the foam starts to form:

The foam density is 130 kg / m ³ .

Example) 2

As example 1; 3 parts by weight of 2-hydroxypropanal oxime are added as a blowing agent to 100 parts by weight of the polyol mixture (component A).

103 parts by weight of component A and 147 parts by weight of component B are reacted according to the process described in Example 1 and produce a free foam with a density of 177 kg / _m3 .

Example 3

As in Example 1; 3 parts by weight of 3-hydroxy-2-methyl-butanal-oxime are added as a blowing agent to 100 parts by weight of the polyol mixture (component A). 103 parts by weight of component A and 146 parts by weight of component B are reacted by the process described in Example 1 and produce a free foam with a density of 107 kg / m ³ .

Example 4

As example 3; the 3-hydroxy-2,2-dimethylpropanal oxime (primary OH group) isomeric to the 3-hydroxy-2-methylbutanal oxime (secondary OH group) is used as the blowing agent.

Example 5

As example 1; 4 parts by weight of 4-amine-top-zaldoxime are added as a blowing agent to 100 parts by weight of the polyol mixture (component A). 104 parts by weight of component A and 146 parts by weight of component B are reacted by the process described in Example 1 and give a free foam with a density of 218 kg / m ³ .

Example 6

80 parts by weight of a difunctional polyether of hydroxyl number 28, which was obtained by addition of propylene oxide and ethylene oxide to propylene glycol, 12 parts by weight of a trifunctional polyether of hydroxyl number 35 and an average molecular weight of 4800, which by addition of propylene oxide and ethylene oxide Trimethylolpropane was obtained, 20 parts by weight of ethylene glycol, 2 parts by weight of trimethylolpropane, 0.015 parts by weight of tin dibutyldilaurate, 0.3 parts by weight of triethylene diamine and 2.6 parts by weight of 3-hydroxybutanol oxime as blowing agents Component A mixed.

Component B consists of a semiprepolymer of bis (4-isocyanatophenyl) methane and dipropylene glycol with an NCO content of 22.8% by weight. 117 parts by weight of component A and 148 parts by weight of component B are mixed intensively with a two-component metering mixer. This foamable reaction mixture is immediately entered into an open paper form (for dimensions, see Example 1). With the onset of foam formation, there is a start time of 18 seconds.

variant

After mixing, the same amount of components A and B is introduced into a plate-shaped, vertically standing tool heated to about 80 ° C. via a spout at the next position. The plate-shaped molding (height = 200mm, width = 200mm, length = 10mm) can be removed after 3 minutes of mold life. The density is 630 kg / m ³ . The plate has a surface hardness of 54 Shore D.

Claims (8)

1. Mixtures incorporating aldoximes as blowing agents and containing

A) polyols or polyol mixtures liquid at temperatures below 45° C and having an average molecular weight of from 400 to 10,000 and, dissolved therein,

B) from 0.1 to 20% by weight and preferably from 0.2 to 8% by weight of an incorporable aldoxime reactive blowing agent corresponding to the following formula

in which

X represents -OH, -COOH, -NH₂ (amino bound to aromatic radicals only), -NHR', where R' is a C_l-C₈-alkyl group (bound to aromatic radicals only); preferably the OH-group, particularly in the form of a secondary OH-group, and

R represents an aliphatic, optionally branched radical containing from 1 to 9 C-atoms and preferably from 1 to 4 C-atoms, a cycloaliphatic radical, optionally containing an -0-atom in the ring, an aromatic radical or an araliphatic radical in which the aliphatic radical is attached to the aromatic nucleus by an oxygen atom.

2. A mixture as claimed in Claim 1, characterized in that the polyol or polyol mixture is liquid at room temperature.

3. A mixture as claimed in Claims 1 and 2, characterized in that the polyol or polyol mixture has an average molecular weight of from 600 to 4000.

4. A mixture as claimed in Claims 1 to 3, characterized in that X is a hydroxyl group and R is an aliphatic or cycloaliphatic radical containing from 1 to 9 C-atoms.

5. A mixture as claimed in Claims 1 to 4, characterized in that X is a secondary hydroxyl group and R is an aliphatic radical containing from 1 to 4 C-atoms.

6. A mixture as claimed in Claims 1 to 5, characterized in that

is used as the incorporable aldoxime reactive blowing agent.

7. The use of the mixtures claimed in Claims 1 to 6 of (A) polyols or polyol mixtures liquid at temperatures below 40° C and having an average molecular weight of from 400 to 10,000 and, dissolved therein, (B) from 0.1 to 20% by weight and preferably from 0.2 to 8% by weight of an incorporable aldoxime reactive blowing agent corresponding to the following formula

for reaction with polyisocyanates, optionally in the presence of other compounds having a molecular weight in the range from 62 to 10,000 and preferably in the range from 62 to 400 and containing NCO-reactive H-atoms and, optionally, other auxiliaries and additives for foaming the reaction mixtures by C0₂ from the incorporable aldoxime reactive blowing agents to form polyurethane foams.

8. The use of the mixtures as claimed in Claim 7, characterized in that polyols or polyol mixtures liquid at room temperature, based on polyethers and having average molecular weights of from 600 to 4000 and from 0.2 to 8% by weight of incorporable aldoxime reactive blowing agents

in which X represents a secondary hydroxyl group and R is an aliphatic radical containing up to 4 C-atoms, are used for forming the polyurethane foams.